title: The inhibitory effects of a rhamnogalacturonan I (RG-I) domain from ginseng pectin on galectin-3 and its structure-activity relationship.
abstract: Pectin has been shown to inhibit the actions of galectin-3, a β-galactoside-binding protein associated with cancer progression. The structural features of pectin involved in this activity remain unclear. We investigated the effects of different ginseng pectins on galectin-3 action. The rhamnogalacturonan I-rich pectin fragment, RG-I-4, potently inhibited galectin-3-mediated hemagglutination, cancer cell adhesion and homotypic aggregation, and binding of galectin-3 to T-cells. RG-I-4 specifically bound to the carbohydrate recognition domain of galectin-3 with a dissociation constant of 22.2 nm, which was determined by surface plasmon resonance analysis. The structure-activity relationship of RG-I-4 was investigated by modifying the structure through various enzymatic and chemical methods followed by activity tests. The results showed that (a) galactan side chains were essential to the activity of RG-I-4, whereas arabinan side chains positively or negatively regulated the activity depending on their location within the RG-I-4 molecule. (b) The activity of galactan chain was proportional to its length up to 4 Gal residues and largely unchanged thereafter. (c) The majority of galactan side chains in RG-I-4 were short with low activities. (d) The high activity of RG-I-4 resulted from the cooperative action of these side chains. (e) The backbone of the molecule was very important to RG-I-4 activity, possibly by maintaining a structural conformation of the whole molecule. (f) The isolated backbone could bind galectin-3, which was insensitive to lactose treatment. The novel discovery that the side chains and backbone play distinct roles in regulating RG-I-4 activity is valuable for producing highly active pectin-based galectin-3 inhibitors.
authors.affiliation: School of Life Sciences, Northeast Normal University, Changchun 130024, China.
authors.forename: Xiaoge
authors.initials: X
authors.lastname: Gao
authors.affiliation: School of Life Sciences, Northeast Normal University, Changchun 130024, China.
authors.forename: Yuan
authors.initials: Y
authors.lastname: Zhi
authors.affiliation: School of Life Sciences, Northeast Normal University, Changchun 130024, China.
authors.forename: Lin
authors.initials: L
authors.lastname: Sun
authors.affiliation: School of Life Sciences, Northeast Normal University, Changchun 130024, China.
authors.forename: Xiaoxia
authors.initials: X
authors.lastname: Peng
authors.affiliation: School of Life Sciences, Northeast Normal University, Changchun 130024, China.
authors.forename: Tao
authors.initials: T
authors.lastname: Zhang
authors.affiliation: School of Life Sciences, Northeast Normal University, Changchun 130024, China.
authors.forename: Huiting
authors.initials: H
authors.lastname: Xue
authors.affiliation: School of Life Sciences, Northeast Normal University, Changchun 130024, China. Electronic address: taigh477@nenu.edu.cn.
authors.forename: Guihua
authors.initials: G
authors.lastname: Tai
authors.affiliation: School of Life Sciences, Northeast Normal University, Changchun 130024, China. Electronic address: zhouyf383@nenu.edu.cn.
authors.forename: Yifa
authors.initials: Y
authors.lastname: Zhou
mesh_terms: D001798:Blood Proteins; D002236:Carbohydrate Conformation; D002448:Cell Adhesion / Q000187:drug effects; D037502:Galectin 3 / Q000037:antagonists & inhibitors / Q000378:metabolism*; D037161:Galectins; D006801:Humans; D019169:Jurkat Cells; D009363:Neoplasm Proteins / Q000037:antagonists & inhibitors / Q000378:metabolism*; D009369:Neoplasms / Q000188:drug therapy / Q000378:metabolism*; D005894:Panax / Q000737:chemistry*; D010368:Pectins / Q000737:chemistry / Q000494:pharmacology; D013329:Structure-Activity Relationship
chemical_list: D001798:Blood Proteins; D037502:Galectin 3; D037161:Galectins; C428445:LGALS3 protein, human; D009363:Neoplasm Proteins; C042491:rhamnogalacturonan I; D010368:Pectins
keywords: Carbohydrate Structure; Carbohydrate-binding Protein; Galectin; Galectin-3 Inhibitors; Ginseng Pectin; Oligosaccharide; Polysaccharide; Rhamnogalacturonan I; Structure-Activity Relationship